1. Field
Embodiments of the invention relate to the field of Mobile IP; and more specifically, to recovering mobility agent information.
2. Background
Mobile IP is a protocol described in Request for Comments 3344, August 2002, which allows laptop computers or other mobile computing units (referred to as mobile nodes herein) to roam between various sub-networks at various locations, while maintaining Internet and/or WAN connectivity. Mobility agents (e.g., home agent, foreign agent) provide Mobile IP functionality. In a typical Mobile IP network, each mobile node is identified by its home address (assigned by a home agent), regardless of its current point of attachment to the Internet. While situated away from its home, a mobile node is also associated with a care-of address (provided by a foreign agent), which indicates its current point of attachment for reachability. While a mobile node is away from its home and connected to a foreign network it requests registration through the foreign agent to the home agent. If the registration is successful, when the mobile node's home network receives packets addressed to the mobile node, the home agent will send those packets, over a tunnel, to the foreign agent which in turns forwards the packets to the mobile node. When the mobile node is sending packets, the foreign agent may employ reverse-tunneling and send the packets to the home agent who in turn forwards the packets to their destination, or the foreign agent may directly forward the packets to their destinations. When the mobile node is successfully registered, the mobile node has started a Mobile IP session. When the mobile node is deregistered (e.g., the bindings for the mobile node have been removed), the Mobile IP session has ended. Typically, if a mobility agent restarts, the mobility bindings stored in the mobility agent is lost.
The Mobile IP protocol describes communicating control messages between the mobility agents. For example during registration of a mobile node, a Mobile IP registration request message and a Mobile IP registration reply message are typically transmitted between a foreign agent and a home agent. At any given time a mobility agent (either a foreign agent or the home agent) may stop providing service to the mobile node. The mobility agent that wishes to stop providing service may send a registration revocation message, described in Request for Comments 3543, August 2003, to the peered mobility agent (e.g., a foreign agent may send a registration revocation message to the home agent). The revocation message informs the receiving mobility agent that the sending mobility agent is stopping service to the mobile node. The mobility agent that receives the registration revocation message associated with a mobile node may remove the mobility bindings for that mobile node.